The present invention relates generally to a three dimensional model display system for use in a machine tool, and more specifically to a real time three-dimensional workpiece shape display system of the type capable of displaying the shape of a workpiece on a real time basis as the workpiece is cut into a desired shape by a tool.
In the field of computerized numerical control systems employed in a machine tool, servo control devices have made remarkable advance with the rapid progress of hardware and software technology in the computer industry. A technique for graphically describing three-dimensional models as well as two-dimensional models has been evolved from a wire frame method in which only the contour of an object is drawn, into a solid method in which the surface of an object is described.
With reference to FIG. 1, there is illustrated a typical three-dimensional display system wherein an electronic hardware utilizes several input and output functions, but performs no active functions in the sense of closing servo loops, as described in U.S. Pat. No. 5,926,389 to James E. Trounson, entitled xe2x80x9ccomputer control system for generating geometric designxe2x80x9d. An interface card includes up/down counters which accumulate pulses from optical encoders attached to motors, to allow a micro processor to read the position of the motors. In addition, the interface hardware includes counters which are loaded by a central processing unit (CPU), to send a fixed pulse width modulation (PWM) signal to power boards. Another counter within the interface card circuitry is loaded with a value which thereafter causes the card to produce a fixed frequency pulse. A deadman timer on the interface card is periodically loaded by the CPU. In order to sequentially access the respective one of six axes, a pointer latch on the interface card is rippled each time a PWM count is loaded into one of the counters. The output from this pointer latch indicates which one of the six axes is to receive the PWM signal. The amount of input/output (I/O) space required is thereby reduced because all sets of I/O ports are at the same physical address for the CPU, but are individually selected via the pointer latch. With reference to the software architecture diagram of the prior art system referred to above, the software is divided into four distinct tasks. Three of these tasks are invoked periodically through hardware generated interrupt requests which occur at the rates, e.g., 6000 Hz, 60 Hz and 10 Hz. The fourth task is the foreground task which operates whenever no hardware interrupts are pending or active. All of the tasks have access to a common shared memory.
One drawback of the above-mentioned prior art three-dimensional display system is that, in order to display on a display screen the three-dimensional model in a computer incorporating only one microprocessor, the system has to rely upon a computer aided design (CAD) program which is incapable of displaying the present contour of a workpiece on the display screen on a real time basis as the workpiece is cut by a tool.
The prior art three-dimensional display system as set forth above is also disadvantageous in that it requires a huge memory for storage of the CAD program, which would render the system costly and bulky.
It would be thus highly desirable to provide a real time three-dimensional display system for use in a machine tool which eliminates those shortcomings found in the above-noted and other prior art systems.
With the deficiencies inherent in the prior art taken into account, it is an object of the invention to provide a three-dimensional model display system for use in a machine tool which can display the geometrical shape of a workpiece on a real time basis as the workpiece cutting operation proceeds without resort to any computer aided design program.
Another object of the invention is to provide a three-dimensional model display method which enables the geometrical shape of a workpiece to be displayed to the view of an operator on a real time basis as the workpiece is cut by a tool in a numerical control machine tool.
According to one aspect of the invention, there is provided a system for real time three-dimensional model display for use in a machine tool, comprising: i) a plurality of motors each capable of providing relative movement between a tool and a workpiece along an associated one of multiple axes; ii) servo means for controlling said motors; iii) a numerical controller coupled to said servo means for transmitting target three-dimensional coordinates of points stored in a memory to said servo means such that said motors can be caused to move into the target coordinates of points, and for receiving actual three-dimensional coordinates of points fed back from said motors; and iv) an image processor for receiving the actual three-dimensional coordinates of points from said numerical controller and directly transmitting said actual three-dimensional coordinates of points to a display screen so as to achieve real time workpiece shape display based on the actual three-dimensional coordinates of points.
According to another aspect of the invention, there is provided a method for real time three-dimensional model display in a machine tool, comprising: i) providing a plurality of motors each capable of providing relative movement between a tool and a workpiece along an associated one of multiple axes; ii) providing servo means for controlling said motors; iii) causing a numerical controller to transmit target three-dimensional coordinates of points stored in a memory to said servo means such that said motors can be caused to move into the target coordinates of points, and to receive actual three-dimensional coordinates of points fed back from said motors; and iv) allowing an image processor to receive the actual three-dimensional coordinates of points from said numerical controller and to directly transmit said actual three-dimensional coordinates of points to a display screen so as to achieve a real time workpiece shape display based on the actual three-dimensional coordinates of points.